Does Wood Chip Mulch Tie Up Nitrogen & Increase Nitrogen Fertilization Requirements?

Hi. Today I’d like to talk about an often debated topic – does wood chip mulch tie up nitrogen in the soil and increase nitrogen fertilization requirements? This debate arises from the fact that bacteria need nitrogen to decompose organic matter. And because wood chips have a high carbon to nitrogen ratio, there’s concern that there isn’t sufficient nitrogen in wood chips themselves for decomposition to take place, and bacteria will utilize nitrogen in the soil instead. It turns out that there’s some debate even among experts on this topic, but one thing they agree on is that nitrogen depletion occurs only on the surface of the soil, and as a result does not impact plants with roots that extend below the surface. This, of course, assumes the wood chips are being used only as mulch and are not being mixed into the soil, which would tie up nitrogen below the surface. So, established perennials would not be negatively affected, nor would tomato transplants, whose roots are buried well below the surface. But what about annual vegetable seedlings with very shallow roots? Will they be affected by possible nitrogen depletion? There’s some disagreement here among the experts I consulted. For example, Jeff Gillman doesn’t think the depletion is significant enough to worry about. In “Decoding Gardening Advice”, he writes “The truth is that some nitrogen from the top layer of soil is used up when wood chips are initially broken down by bacteria. But this nitrogen loss is likely to affect only the most tender annuals, and even they probably will not sustain any permanent injury.” Gillman goes even further, and says the advice that extra nitrogen fertilizer is needed when using wood chip mulch is “just wrong”. Dr. Linda Chalker-Scott, however, is a little more cautious when it comes to small seeded annuals. In her article “Wood Chip Mulch: Landscape Boon or Bane?”, she states “My hypothesis is that a zone of nitrogen deficiency exists at the mulch/soil interface, inhibiting weed seed germination while having no influence upon established plant roots below the soil surface For this reason, it is inadvisable to use high C:N mulches in annual beds or vegetable gardens where the plants of interest do not have deep, extensive root systems.” One thing both experts completely agree on, however, is that over time wood chip mulch adds more nitrogen to the soil than it takes. According to Gillman, “The confusion over whether wood chip mulches cause nitrogen deficiencies that harm plants persists, despite numerous studies demonstrating that serious depletion of nitrogen is not taking place. In fact, many studies have indicated that just the opposite occurs. As wood mulches decompose, they enrich the soil with many nutrients, including nitrogen.” This is consistent with our experience. We’ve never noticed any nitrogen deficiencies when using wood chip mulches, despite the fact we use no store-bought nitrogen fertilizers. If you’re still concerned about nitrogen depletion, however, you can always add fast decomposing high nitrogen materials like grass clippings or comfrey to your mulch. They’ll provide nitrogen to aid in the decomposition of the wood chips and potentially decrease nitrogen depletion on the soil surface. When using wood chips, we typically apply a few inches, and are always careful not to mix them into the soil, as this would cause nitrogen depletion below the surface where plants need nitrogen. We use wood chips from the municipal wood chip pile, which contains a wide variety of tree species. Allelopathic trees that suppress the growth of other plants are not common in our area, so we use the wood chips without worry. However, if you live in an area where allelopathic trees like Black Walnut or Eucalyptus are common, you’ll want to avoid using them as mulch. When transplanting vegetable seedlings into the garden, I brush the wood chips aside, and plant the seedling in the soil with a little bit of compost, taking care not to mix the chips into the soil. Similarly, when planting seeds, I create a small furrow in the wood chips, fill it with compost, and plant the seeds in the compost. So, I wouldn’t let concerns about nitrogen depletion stop me from using wood chip mulch, and I wouldn’t use extra nitrogen fertilizer when using them. They help control weeds, retain water, moderate soil temperatures, and over time add nutrients, including nitrogen, to the soil. Well, that’s all for now. Thank you very much for watching, and until next time remember you can change the world one yard at a time.


  1. I hate it when you go to the store and buy potting soil that is full of mulch. It's good for outdoor gardens but I hate picking big 2 inch long shards of wood out of my plant pots.

  2. You're not as daft as you look you Patrick are you! Thank God eucalyptus trees aren't as common as they used to be here in Wakefield. I stopped smoking yesterday. I've smoked 40 a day for nearly 30 years now and have been spending £120 a week on the ruddy things not to mention the deterioration in my health. I have to admit I'm going through sheer hell at times and only the thoughts of others can save me from this anguish.

  3. Thanks to your videos, I got intrested in mulching my garden a lot…;) But I can't find many wood chips round my town( I live in Ivano-Frankivsk,Ukraine)–only sawdust…..can it be used as well??With same effect on soil………Thank YOU

  4. i am about to order some woodchips for my orchard. will it help if every few weeks i lay some coffee grounds on the top, especially during the rainy season.  i am assuming this will help the decomposition in the years to follow.

  5. After transplanting seedlings to my raised beds, I put down a layer of grass clippings, followed by wood chips. The grass clippings feed the young plants to get them established and also provide extra nitrogen at the soil to wood chip interface. The wood chips then keep my beds moist during the hot dry summers, reducing watering needs. I use compost tea once month. Never once had a plant looking nitrogen deficient.

  6. And note that long-time practitioners move the topmost mulch aside and plant into the semi-composted material and soil below.

  7. I enjoyed your video. After watching your video back in January of 15, I decided to try a unscientific experiment, I have a 6'x6'x1' deep wood chip pile that I had screened down to about 1/4'' size. So in May of 15, I planted an arugula plant from a nursery, it came in a 1''x2 '' pot, it was a small plant. I took a 1/4 cup of worm castings, 3/4 cup of compost, and mixed it together. I dug down into the wood chip pile too 3'' above the ground, put in the mix and planted the arugula plant in the middle, and put wood chips all around it. The plant looked sad for about 3 weeks, I thought it was going to pass away to the great beyond. But as it turn out, it not only lived, but flourished. While my arugula in my garden ceased to produce latter that year, the one in the wood chips kept going, finally in December I pulled the plant to see what was going on, the roots went through the wood chips and into the ground, with a few roots in the wood chips, and the part of the root that was in the wood chips before going into the ground seem to be a bit larger in diameter. So much for wood chips tying up nitrogen.

  8. Woodchips does tie up nitrogen but you will get it back the following year. Normally I compost my chis with manure for a year before using them. However using them as a mulch I water with a bit of liquid fish fertilizer 3 times a year and have never had a problem. God Bless

  9. excellent presentation and comments, when y'all say layer of grass clippings do you actually mean "lawn" clippings because my "lawn" is lots of weeds, grass, crabgrass, hideous nutgrass, dandelion, etc. etc. some have seedheads do you mean grass specifically or any clippings?

  10. I just saw a video from a different gardener that showed how a local farm used a thick base of wood chips with a depth of about 1 foot(which breaks down to much less over time) and then put a thick layer of compost(about 8 inches deep) which he planted his crops in. The purpose of the wood chips was to retain water and act as a natural fertilizer creating very good soil structure and health. However, I was wondering if the wood chips would rob nutrients from the plants. The plants were incredibly healthy looking and i think that the thick layer of compost prevented the wood chips from depleting the plants intake of nitrogen from the soil.

  11. i put down wood chips from a local tree trimmer service in october, it is now april and i have dust piles here and there but other piles look like something poured in a small area and dried on top. im not sure what this is. can you help? is it something that happen naturally or something else?

  12. Because wood chips create a good bed for earth worms this would seem to increase nitrogen just under the surface through the worm castings, plus aerate the soil.

  13. Hello OneYardRevolution, love your videos and info. We have access to free wood chips from our council which is basically a mixture of pine trees and eucalyptus trees. Can I use this as a mulch in my garden? Will it affect the acidity/alkalinity of the soil? Please comment. Thanks.

  14. Thank you for the information. I just had two large truck loads of wood chips delivered. It's a mix of chips and leaves( oak I believe.) I was wanting to create paths with it. I was considering adding it to my raised beds also when I tuck them away this fall also. This video give me a bit more confidence in doing so. Thank you.

  15. What about adding used coffee grounds to increase the nitrogen for the wood chips. I'm just starting out with the whole wood chips thing. I've learned a lot through your videos. Thanks for your help.

  16. Basically, nitrogen will be lost because of uptake by bacterial communities whose populations grow in conjunction with the added carbon from wood chips, then these bacteria die and release that nitrogen back into the soil food web where hopefully plants will take up enough of it before soil fauna does. The answer to the debate is (1) depends on timing of crops & soil amendments (2) depends on the amount of carbon and nitrogen you're adding. The general rule of thumb is that when C:N ratio of organic matter in soil is over 30:1, bacteria will start using up nitrogen from the soil.

  17. Makes sense, the nitrogen the wood uses to break down is still there, just not available, till the wood finishes breaking down, then it is released back into the soil.

  18. Oh how I miss the muni chip pile! My beds have always done better with woodchips, burying animal manure and compost with a woodchip covering has been great. Creating a mycelium mat, retaining moisture, and reducing weeding is well worth a little nitrogen.

  19. Hey Mr Dolan, Here in my place I can't find wood chips but have lots of wood shavings (very thin) available. How do I put it to good use?? Also I have few questions:

    Unlike woodchips, if wood shavings are applied as a mulch layer should I add a nitrogen rich material like tea leaves(which I get in abundance here) or/and other green leaves , to prevent nitrogen depletion??

    Does a thick layer of wood shavings when moist give rise to fungal growth and hence lead to root rot??

  20. Hi Patric I saw a lot of mycelium thread as you moved your wood chip around with your hand, it is as necessary as nitrogen bacteria to soil

  21. Hi Patric i live in Nevada and i ask same of my friends how to get the wood chips for my garden and they toll me is not good for my garden because is going to bring more scorpions to my property,is maybe true ? in this area is a lot scorpions

  22. Hi. Have been wood chip mulching for many years now. I recently had a massive failure for the first time. The wood chips hold moisture and new seedlings developed damping, or dampening.

    Pulling the wood chips back and providing a clear area while they developed fixed it.


    The seedlings were planted into raised mounds – I think the side walls aided in nitrogen depletion and impacted.

    Also I am not entirely sure about this thesis on eucalyptus. I have used it extensively for many years and it worked fine (I added nitrogen and rock dust).

  23. The nitrogen that would be lost from the soil is Nitrogen in gas form & actully binds to the carbon in the woodchip mulch, hence why there is no difference to the plants, however this nitrogen is actually stabilised by the carbon into a usable form for plants, over time, which is why woodchips are best when they come with leaves through them for instant nitrogen release to the soil too.

  24. Friend of mine mulched in wood chips and he said he had a problem with nitrogen depletion  I hear mulching in sawdust is not good

  25. I was given composted wood chips. they are completely broken down into a fine black soil. all that was in this were wood chips. I'm wondering if it's safe to add to my vegetable garden. I didn't see any bugs living in the compost but there were some weeds growing on top of the pile when I picked it up. I guess the absence of bugs has me worried about using it.

  26. Mr> Doolan, You mentioned not to use black walnut chips. I have a black walneu right near my future garden area. Will the leaves also prevent plant growth?

  27. Great video. I have a lot of pine wood chip in my area for free. I would like to know if it is good choice to use for mulch? I've heard it would bring in the termites. Please help!

  28. Microbes consume the carbohydrates for energy. One waste product of respiration is CO2. So gradually the C/N gets smaller and the overall proportion of N increases. Makes sense to me. THANK YOU for thinking about this independently.

  29. Hi Patrick, Thanks for your work. The comments are as useful as the video so thanks again for your support. We've been getting whole tree chipped wood turning up from our local arboricultural firm. Our garden has swallowed probably 4 tonnes of pine woodchip (paths / mulch), 4 tonnes of cedar redwood chip (we use this for paths/ acid established perrenial shrubs) and 6 tonnes of oak (for mulch). We were recently gifted use of another 10 yard square plot next to my garden by my neighbour where we have put a keyhole hugelkulture bed and a huglekulture long bed of about 5 yards in length as it is nearly full sun whereas my plot is 65% sun 35% shade. Some questions – Do you plant raised beds in guilds? When mulching we are trying to use deep mulching to grow soil over a number of years where we have a slope that we want to flatten out into a stepped bed. Are their any contraindications to watch out for. I read one of the comments about 5 inch max depth around trees and already an acer and magnolia has suffered with wilting and scorced leaves after we have probably over mulched this bed with the redwood and either pH or O2 has affected the health. Any tips on what to watch for?

  30. Great video! As always! You are an inspiration. Wood chip mulch is definitely great for weed suppression, but this beneficial effect is not explained by a zone of nitrogen depletion as Scott hypothesized. There is a temporal zone of N def at the soil/mulch interface. However, this is an associated phenomena, not a causative variable. Experimentally, Scott's hypothesis is contradicted by the fact that many "weed" seeds readily germinate in plenty of low N environments.. such as sand, peat moss, wet paper towels, wet cardboard, petri dishes, even various non-nutritive laboratory media. There is pretty much zero bioavailable nitrogen in coconut coir, but we can germ seeds in it all day long. Wood chip mulch likely suppresses weeds when there is enough depth of mulch to block out sunlight, and also creates some heat as it breaks down. If only a small depth of woodchip mulch is applied, weeds grow right through it. Wood chip mulch suppresses weeds the same way smothering them with a black tarp does…. heat and light starvation, nothing to do with N. Cheers

  31. How do you go about adding compost or manure to this? Do you just layer it on top? Won't that eat up the nitrogen?

  32. I have access to free pine sawdust, untreated. Does anyone have experience with that as a mulch? tiny woodchips right?

  33. hello Patrick thanks so much for your videos..
    my question is this .. am new to gardening i leave in south Florida and last year i started mulching with eucalyptus wood chips the idea was to to keep the soil moist and this wood chips deter insects … to be honest i don't think it was a good idea because ever since they have problem bearing fruits and they don't look pretty good please give me your advise …

  34. Hi. our city has free chips available and I've been scooping them onto my garden. I had a large area of bare soil. So. I put down cardboard on the soil, then put the chips on that. (I dig down to get the mostly decomposed product) The majority of this free mulch is in fact eucalyptus. Should I be concerned about my established tomato plants? To plant them, I clear away all mulch, cut the cardboard, add compost and nutrients, some planting mix, minerals, cover with more compost, straw, and then recover with the rotted mulch. Not sure if I should be concerned. what do you think?

  35. So we have loads of eucalyptus trees round us, they do not dominate, but are common, I was going try to and have local chips dropped off, (we have very sloped areas, front and back alley so not sure it will work). Now I am wondering of I should, and what I should do in there absence for sheet mulching. I guess for the paths it would be fine, but below garden beds… I cant imagine having to buy them.

    Do the leaves also have this attribute?

  36. hi can you get some help from you? I added bark mulch around my fruit trees and roses about 5 months ago. I started to get interested in woodchips so I laid wood chips on top of the bark as I didn't have the time to remove the bark. I also bought worm casting, compost and rock dust. Can i add the compost, rock dust and worm casting on top of the of bark and woodchips to help it decompose faster? should I add nitrogen to it as well? thanks

  37. I have a layer of 10-12 inches of woodchips on my orchard, and my mistake was thinking they didn’t need extra nutrients because of the heavy mulch. Ie been adding compost tea, and they are now thriving.

  38. Not being a scientist or an expert I found two simple solutions to wood chips causing nitrogen deficiency in the soil. I soak them in a solution of one part urine and nine parts water. The other is to apply that solution to the area mulched or has wood chips mixed in the soil. Urine turns into ammonia and bacteria turn it into nitrates which the plants  use. It is the same principle as used in aquaponics only it is in the soil and not in water. The same bacteria that do the converting live in both places.

    The problem with most scientists and experts is they have a limited range of expertise and seldom look outside of it for solutions. From what I read, I think they spend most of their time quoting other experts who quote them. To find solutions a person has to have a wide range of knowledge.

    The carbon to nitrogen ratio is 1:1 for urine and 500:1 for wood chips without green material. Why not combine them to get close to the ideal 30:1 ratio.  Urine is free and every person produces gallons of it every week. Why not put it to a practical use instead of flushing it into the sewers and polluting the lakes streams and oceans. Of course the synthetic fertilizer companies wouldn't like that because it would cut into their profits and that is a no, no.

    Urine is sterile unless you are sick or drugs (prescription or not). There is a lot less chance of getting sick from using it for fertilizer as there is from eating the toxic frankenfoods pushed on us today or the toxic chemicals in vaccines.

  39. do you no what point wood stops robbing nitrogen and starts giving? once its fully broken down? half way? when its all black? cheers

  40. at the end of the year last year I mixed in my wood chips not knowing that they would cause problems. they were fine wood chips that you would use for landscaping. What should I do to counteract it this year?

  41. Straw bale gardening also relies on the release of nitrogen from within the bales as bacteria break down the inner material. This typically takes about two weeks when you water them thoroughly and then apply a high nitrogen fertilizer to kick off bacteria consumption. Once the bales get going, my experience is that they are a great medium for growing tomatoes, peppers, potatoes, flowers and other vegetables. I've heard complaints from some people who tried planting straight into uncomposted or inadequately composted straw bales that their plants basically and died. I suspect it is because bacteria were using all the available nitrogen to consume the wet straw, taking nutrients away from the seedlings. if they had waited for mushrooms to pop up I think they would have gotten better results.

  42. I would think that if you put wood chips on the surface of the soil they would not have much effect on deep rooting plants. But if next year you worked the same chips into the soil before they began releasing their nutrients, they might rob the roots of next year's plants of nitrogen. I do use wood chips on top of container gardens but at the end of the season I scoop them off into a pile for reuse on the ground or on top of next year's pots. For my raised beds and ground surfaces I generally use fast decaying mulch like old straw or coacoa shells.

  43. If you have a couple of raised beds, put 3" of any chips as mulch. Simply add more during the year to keep a thick layer. Pull them back to expose soil when planting. Use started plants when you can. Now, if you're like me and have an acre or more it just isn't practical. I use a plow,disc, and rototiller to prepare the beds for plastic mulch. In this system using wood chips between the rows was horrible. The weeds came up through the wood chips, which cost $350 each for 3 trucks full. Worse was it took $200 in urea to ballance out the carbon when it was turned in. I added 7 tons of manure and I still had to inject liquid fertilizer in the drip system. So, small time, wood chip good. Large production sized, wood chip bad!

  44. What if I tilled in fresh wood chips from my municipal center in my vegetable garden. should I add nitrogen. i'm planting it heavy clay soil, just started composting this year add tilling in fresh grass clippings to 2/3 of my garden, only planting a 1/3 of our garden this year to try and help amend what if can for free or very cheap. we have access to our rabbits poop and 1-2 cubic yards of pig manure from our neighbor for the winter. I was planning on doing the 4-8 inches of local wood chips to decompose with mushroom spores and red wiggler( compost) worms with nightcrawlers. my garden right now is 20X75. I cant afford to buy compost to cover it, looking for a quick easy method to loosen and add nutrients. when tomatoes are done I will till and plant buckwheat and maybe a alfalfa then finish off with a winter rye. what would you. the viewee and the viewer suggest. also what are the best veg garden forums??

  45. Question, how do you reverse the negative effects and aftermath of tilling wood chips 6 to 10 inches beneath the surface. Here’s what I did. Last fall (2107) I tilled my wood chips into my 80 ft. X 60 ft garden, this was before I knew any better and that the wood chips consumed nitrogen underground and it was pretty much the Worst thing I could do to my once healthy and nutrient rich soil. My garden is mainly tomato’s, peppers peas, cucumbers, celery and lettuce. This growing season I suffered the consequences of my mistake. All of my plants stayed alive but they barley grew and most plants did not produce any fruits, for example the tomato plants that did produce literally had 2 to 5 tomatoes all season.
    Any suggestions on how to speed up and reverse the negative effects caused by the underground wood chips?

  46. Yarrow,Comfrey,Red Mustard,Carob tree..plants will help break woodchip down,but woodlice n fungus a natures preferred decomposers( the SOUTHERN HEMISPHERE anyway)

  47. I think it did but it’s depend what is it. I planted my squash and potato in my wood chips mulch and it never grow big but while my green beans and peas that I planted from seed direct and they loves the wood chips

  48. Our trials showed we didn't really need to add much extra nitrogen to offset tilling wood chips into the fields. See:

  49. Nobody has mentioned using urine. Wouldn't adding urine to the woodchips address the nitrogen issue easily, cheaply, and using a resource that is abundant?

  50. What about a 50/50 shaving/soil mix if the wood shavings have been soaked in comfrey prior to mixing? I intend to do this experiment with tomatoes in the coming 2019 season 👍

  51. I know this is an old video, but I wanted to comment how much I appreciate a sensible, balanced, and rational discussion of alternative gardening methods. Most others are either wildly in favor of the use of wood chip mulch, or take the mainstream approach of eschewing their use in veggie beds completely. You offer valid pros and cons, clearly citing sources, and then present your own experiences and opinions. Excellent information!

  52. Thank you dear brother for sharing your knowledge 🙏 We have germinated healthy plants in a potting mixture of 50% sand, 45% saw dust & 5% vermicompost. The plants have sprouted and are healthy though the first batch went a bit lengthy to seek out sun. We have transplanted them last week, will update you further. Can see the pics on Instagram @nikzboz

  53. I got a ton of pine chip mulch for free, and I’m so confused on how to use it!! 😩 do I have to lime it first??

  54. How much of a problem could using some slightly allelopathic mulch be… I read a study on Tree of Heaven's phytotoxic effects, and while they found that though ailanthone [Tree of Heaven's main allelopathic compound] was a powerful inhibitor, "Applications of ailanthone equivalent to 0.5 and 4.0 kg/ha completely lost their phytotoxicity within ≤5 d when incubated in the presence of nonsterile soil." I.e. soil bacteria were quite able to break it down, and if those compounds aren't being actively secreted from living root tips — you're just dealing with the chips that are dead tissue? Another study specifically on allelopathic mulch for weed control mentions that red cedars and Pinus sp. chips can be inhibitory also… So meh? Are we going to go to the trouble to avoid any tree that makes tannins or something else cool? Maybe just try to keep your mulch not all of one kind…? Or let it sit and get oxidized a bit perhaps before use.

  55. I think I have this problem. I picked up several yards of compost from my city, and they've been sitting in raised beds for two months now. Can I amend the soil by adding nitrogen? Should I sift out all the woodchips?

  56. If we want to fertilize our plants, can we sprinkle on top of wood chips or should will pull out wood chips on fertilizer in the soil.

  57. Nitrogen depletion is real, and is actually used as a method of weeding a meadow if you want to grow vegetables on it. The depletion lasts for 3 to 6 months. Sometimes you don't see that depletion, because your humus layer had already a ton of nitrogen in the soil, so enough for both the organisms breaking down the wood chips and the plants. That's why people who grow vegetables testify of one nitrogen depletion episode, and then the next year when they add the second layer of woodchips it doesn't happen (or on a shorter period of time). So it definitely exists, but the true answer is "it depends". Of course over the long run, woods whips are immensely beneficial to your soil and plants, it's longer lasting than straw or hay.

  58. I've always mixed wood chips/pine bark mulch into the soil in small amounts when planting shrubs/trees and making beds. I find that the tying up of nitrogen is worth it to get better aeration and slow release fertilizer. I've rarely notice this being an issue when establishing beds/planting trees. In that I generally use well aged compost (mushroom or homemade) thus I've got enough nitrogen to spare. When plants are first getting establish I don't want them to focus on leafy growth but creating a strong root system.

    I've planted numerous bare root fruit trees and shrubs and haven't lost a single one (well I dropped a branch on one when working in the back but I dont count that). And I think the wood chips/pine bark mulch are a big part of it.

    My ratio for my area for a 3 gallon plant my be something like 1 part peat moss, 1 part aged mushroom compost (I have acidic soil so I want some alkaline material) and 2-3 handfuls of woodchips/pinebark mulch. With the hole being twice as wide and twice as deep ending with it roughly 50% higher than the surrounding soil (creating a mound) with the top of the root ball exposed. Then I make sure I have good soil contact and try ti create ridge to allow water to collect. Then a nice hard watering (before planting water the plant… if bare root I soak in water with bit of root hormone overnight).

    I think if I were to use fresh compost (as I never have enough on hand when planting as I generally top dress everything with it the second I have some) I would increase the amount of woodchips because I wouldnt want to burn my roots or have them focus on leafy growth.

  59. All I know is that most of my plants have a lot of beautiful white roots growing above the surface of the dirt into the wood chip mulch. To me that says a lot

  60. add horse urine to compost & increase nitrogen turn your wood chips to a rouge saw dust stack like normal compost about 3 to 6 months it will be composted like normal

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